Fig. 4. Coupled GC–SSR from a short blunt type II trichoid (sbtII-2) sensillum, showing responses elicited by two different extracts: feet and trunk. Electrophysiological responses of the `A' neuron (A,B) to octanal and nonanal, obtained from injection of the feet headspace extract. Responses of the same cell to four FID peaks (upper trace in C), obtained from injection of the trunk headspace extract. Mass spectrometry (MS) analyses identified FID peaks as heptanal, octanal, nonanal and geranylacetone. Some of the compounds are shared between different types of extracts. Lower traces in C and D represent continuous monitoring of spike frequency over time.